Field of the Invention
The present disclosure provides BET bromodomain inhibitors and therapeutic methods of treating conditions and diseases wherein inhibition of one or more BET bromodomains provides a benefit.
Background Art
The genomes of eukaryotic organisms are highly organized within the nucleus of the cell. The long strands of duplex DNA are wrapped around an octamer of histone proteins (usually comprising two copies of histones H2A, H2B, H3, and H4) to form a nucleosome, which then is further compressed to form a highly condensed chromatin structure. A range of different condensation states are possible, and the tightness of this structure varies during the cell cycle. The chromatin structure plays a critical role in regulating gene transcription, which cannot occur efficiently from highly condensed chromatin. The chromatin structure is controlled by a series of post translational modifications to histone proteins, notably histones H3 and H4. These modifications include acetylation, methylation, phosphorylation, ubiquitinylation, and SUMOylation.
Histone acetylation usually is associated with the activation of gene transcription, as the modification loosens the interaction of the DNA and the histone octamer by changing the electrostatics. In addition to this physical change, specific proteins bind to acetylated lysine residues within histones to read the epigenetic code. Bromodomains are small (about 110 amino acids) distinct domains within proteins that bind to acetylated lysine resides commonly, but not exclusively, in the context of histones. There is a family of about 50 proteins known to contain bromodomains, which have a range of functions within the cell.
The BET family of bromodomain-containing proteins (“BET bromodomains”) includes four proteins, i.e., BRD2, BRD3, BRD4, and BRD-t, which contain tandem bromodomains capable of binding to two acetylated lysine residues in close proximity, thereby increasing the specificity of the interaction. BRD2 and BRD3 associate with histones along actively transcribed genes and may be involved in facilitating transcriptional elongation, while BRD4 may be involved in the recruitment of the pTEF-β complex to inducible genes, resulting in phosphorylation of RNA polymerase and increased transcriptional output. BRD4 or BRD3 also may fuse with NUT (nuclear protein in testis) forming novel fusion oncogenes, BRD4-NUT or BRD3-NUT, in a highly malignant form of epithelial neoplasia. Data suggests that BRD-NUT fusion proteins contribute to carcinogenesis. BRD-t is uniquely expressed in the testes and ovary. All family members have been reported to have some function in controlling or executing aspects of the cell cycle, and have been shown to remain in complex with chromosomes during cell division, which suggests a role in the maintenance of epigenetic memory. In addition, some viruses make use of these proteins to tether their genomes to the host cell chromatin as part of the process of viral replication.
A discussion of BET proteins can be found in WO 2012/075456, WO 2012/075383, and WO 2011/054864. A discussion of BET bromodomain inhibitors, e.g., I-BET-151 and I-BET-762, can be found in Delmore et al., Cell 146:904-917 (2011) and Seal et al., Bioorg. Med. Chem. Lett. 22:2968-2972 (2012). Small molecule inhibitors of BET bromodomains have therapeutic potential for the treatment of many diseases and conditions in which BET bromodomains have a role, including cancer. BET bromodomain inhibitors are disclosed in the following U.S. Pat. No. 8,044,042, U.S. Pat. No. 8,476,260, U.S. Pat. No. 8,114,995, U.S. Pat. No. 8,557,984, and U.S. Pat. No. 8,580,957; the following U.S. patent application publications: US 20120059002, US 20120208800, US 2012202799, US 2012252781, US 20130252331, US 20140011862, US 20130184264, US 2013079335, US 20140011862, US 20140005169, US 20130331382, US 20130281450, US 20130281399, US 20120157428, and US 20100286127; and the following international applications: WO 1998011111, WO 2006129623, WO 2008092231, WO 2009084693, WO 2009158404, WO 2010123975, WO 2011054843, WO 2011054844, WO 2011054845, WO 2011054846, WO 2011054848, WO 2011143651, WO 2011143660, WO 2011143669, WO 2011161031, WO 2012075383, WO 2012116170, WO 2012151512, WO 2012174487, WO 2013024104, WO 2013027168, WO 2013030150, WO 2013033268, and WO 2013097601.
Men who develop metastatic castration-resistant prostate cancer (CRPC) invariably succumb to the disease. The development and progression to CRPC following androgen ablation therapy is predominantly driven by unregulated androgen receptor (AR) signaling (Taylor, B. S. et al., Cancer Cell 18:11-22 (2010); Chen, C. D. et al., Nat Med 10:33-39 (2004); Visakorpi, T. et al., Nat Genet 9:401-406 (1995)). Despite the success of recently approved therapies targeting AR signaling such as abiraterone (Stein, M. N., Goodin, S. and Dipaola, R. S., Clin Cancer Res 18:1848-1854 (2012); Reid, A. H. et al. J Clin Oncol 28: 1489-1495 (2010); de Bono, J. S. et al., N Engl J Med 364: 1995-2005 (2011)) and second generation anti-androgens MDV3100 (enzalutamide) (Mukherji, D. et al. Expert Opin Investig Drugs 21:227-233 (2012); Scher, H. I. et al., N Engl J Med 367:1187-1197 (2012)), durable responses are limited, presumably due to acquired resistance. Recently JQ1 and I-BET, two selective small molecule inhibitors that target the amino-terminal bromodomains of BRD4, have been shown to exhibit antiproliferative effects in a range of malignancies (Lockwood, W. W. et al., Proc Natl Acad Sci USA 109:19 408-19413 (2012); Dawson, M. A. et al., Nature 478: 529-533 (2011); Delmore, J. E. et al. Cell 146: 904-917 (2011); Puissant, A. et al. Cancer Discov 3:308-323 (2013)). BRD4 physically interacts with the N-terminal domain of AR and can be disrupted by JQ1 (Delmore, J. E. et al. Cell 146: 904-917 (2011); Puissant, A. et al. Cancer Discov 3:308-323 (2013); Filippakopoulos, P. et al. Nature 468:1067-1073 (2010)).
The identification and therapeutic targeting of co-activators or mediators of AR transcriptional signaling should be considered as alternate strategies to treat CRPC (Attard, G. et al., Clin Cancer Res 17:1649-1657 (2011)). BRD4 is a conserved member of the bromodomain and extraterminal (BET) family of chromatin readers that include BRD2/3 and BRDT. BRD4 plays a critical role in transcription by RNA PolII, by facilitating recruitment of the positive transcription elongation factor P-TEFb (Jang, M. K. et al., Mol Cell 19:523-534 (2005); Yang, Z. et al., Mol Cell 19: 535-545 (2005). Similar to other BET-family proteins, BRD4 contains two conserved bromodomains, BD1 and BD2. Competitive binding of JQ1 or I-BET to the bromodomain pocket results in the displacement BRD4 from active chromatin and subsequent removal of RNA PolII from target genes (Dawson, M. A. et al., Nature 478: 529-533 (2011); Delmore, J. E. et al., Cell 146: 904-917 (2011); Puissant, A. et al., Cancer Discov 3:308-323 (2013); Filippakopoulos, P. et al., Nature 468:1067-1073 (2010); Loven, J. et al., 153:320-334 (2013)) Although most cancer cells express BET-family proteins, it is not clear why only a subset of cell lines from diverse cancers respond to BET-inhibitors (Lockwood, W. W. et al. Proc Natl Acad Sci USA 109:19408-19413 (2012); Mertz, J. A. et al., Proc Natl Acad Sci USA 108:16669-16674 (2011)). Recently, BRD4 was shown to interact with sequence-specific DNA-binding transcription factors in a gene-specific manner (Wu, S. Y. et al., Mol Cell 49:843-857 (2013)). As the genetic and epigenetic landscape differs between tumor types, it is possible that distinct transcriptional regulators that associate with BRD4 might influence the action of BET-inhibitors.
Breast cancer accounts for more than 20% of all cancers in women worldwide. The expression of androgen receptor (AR) is widespread both in ER (estrogen receptor)-positive and ER-negative breast cancers. In ER positive breast cancer adjuvant therapy with ER antagonist tamoxifen or aromatase inhibitors (AIs)—which block conversion of androgen to estrogens, has shown to be effective in inhibiting disease progression. Moreover, direct AR antagonist Enzalutamide (MDV3100) has recently been proposed as a therapeutic modality for AR positive breast cancers.
Despite research directed to BET bromodomains and BET bromodomain inhibitors, the design of potent, non-peptide inhibitors of BET bromodomains remains a significant challenge in modern drug discovery. Accordingly, a need still exists in the art for BET bromodomain inhibitors having physical and pharmacological properties that permit use of the inhibitors in therapeutic applications, especially in humans. The present disclosure provides compounds that bind to BET bromodomains and inhibit BET bromodomain activity.